Question

Write a program in Java according to the following specifications:

The program reads a text file with student records (first name, last name and grade on each line). Then it prompts the user to enter a command, executes the command and loops. The commands are the following:

• "print" - prints the student records (first name, last name, grade).
• "sortfirst" - sorts the student records by first name.
• "sortlast" - sorts the student records by last name.
• "sortgrade" - sorts the student records by grade.
• "end" - exits the loop the terminates the program.

For example, if the input file includes the following data:

John Smith   90 

Sarah Barnes 75

Mark Riley   80 

Laura Getz   72

Larry Smith  95

Frank Phelps 75

Mario Guzman 60

Marsha Grant 85

the program may proceeds as follows (user input is shown in bold face):

Enter command: print

John Smith   90 

Sarah Barnes 75

Mark Riley   80

Laura Getz   72 

Larry Smith  95

Frank Phelps 75

Mario Guzman 60

Marsha Grant 85

Enter command: sortlast

Students sorted by last name

Enter command: print

Sarah Barnes 75

Laura Getz   72 

Marsha Grant 85 

Mario Guzman 60 

Frank Phelps 75 

Mark Riley   80 

John Smith   90 

Larry Smith  95

Restrictions and implementation: Use a regular array (not ArrayList) of objects of class Student to store the student records. Define a class Student that represents a student record (student's first name, last name and grade) and implements the Comparable interface. Use the bubble sort algorithm for sorting objects implementing the Comparable interface. Hint: Define a static instance variable in class Student to specify the type of sorting and use it in the compareTo method to determine what to compare - first names, last names, or grades.

ExtraCredit (maximum 2 points): Implement "add" and "delete" commands for adding and deleting students given their names and grades.

Answer 1

Note: Could you plz go through this code and let me know if u need any changes in this.Thank You
_________________

// students.txt

John Smith 90
Sarah Barnes 75
Mark Riley 80
Laura Getz 72
Larry Smith 95
Frank Phelps 75
Mario Guzman 60
Marsha Grant 85

___________________

// Student.java

public class Student implements Comparable<Student> {
   private String firstname;
   private String lastname;
   private int grade;
public static String command;
   public Student(String firstname, String lastname, int grade) {
       this.firstname = firstname;
       this.lastname = lastname;
       this.grade = grade;
   }

   public String getFirstname() {
       return firstname;
   }

   public void setFirstname(String firstname) {
       this.firstname = firstname;
   }

   public String getLastname() {
       return lastname;
   }

   public void setLastname(String lastname) {
       this.lastname = lastname;
   }

   public int getGrade() {
       return grade;
   }

   public void setGrade(int grade) {
       this.grade = grade;
   }

   @Override
   public String toString() {
       return firstname + " " + lastname + " " + grade;
   }

   public static void setCommand(String command) {
       Student.command = command;
   }

   public int compareTo(Student other) {
       String temp;
       int val=0;
       if(command.equalsIgnoreCase("sortlast"))
       {
           return this.getLastname().compareTo(other.getLastname());
       }
       else if(command.equalsIgnoreCase("sortfirst"))
       {
           return this.getFirstname().compareTo(other.getFirstname());          
       }
       else if(command.equalsIgnoreCase("grade"))
       {
           int ograde = other.getGrade();

           if (getGrade() > ograde)
           val = 1;
           else if (getGrade() < ograde)
           val = -1;
           else if (getGrade() == ograde)
           val = 0;
           return val;
       }
       return val;
   }

}
_______________________

// ReadStudentsData.java

import java.io.File;
import java.io.FileNotFoundException;
import java.util.Arrays;
import java.util.Scanner;

public class ReadStudentsData {

   public static void main(String[] args) {
       String command,fname,lname,str;
       int grade,cnt=0;
       Student sarr[]=new Student[100];
try {
       Scanner sc=new Scanner(new File("students.txt"));
       while(sc.hasNext())
       {
           fname=sc.next();
           lname=sc.next();
           grade=sc.nextInt();

           Student s=new Student(fname, lname, grade);
           sarr[cnt]=s;
           cnt++;
       }
       sc.close();
       /*
       * Creating an Scanner class object which is used to get the inputs
       * entered by the user
       */
       sc = new Scanner(System.in);

       while(true)
       {
           System.out.print("\nEnter command :");
           command=sc.next();
           if(command.equalsIgnoreCase("print"))
           {
               display(sarr,cnt);
           }
           else if(command.equalsIgnoreCase("sortlast"))
           {
               Student.setCommand(command);
       //performing sorting operation
           bubbleSort(sarr,cnt);

               display(sarr,cnt);
           }
           else if(command.equalsIgnoreCase("sortfirst"))
           {
               Student.setCommand(command);
               //performing sorting operation
           bubbleSort(sarr,cnt);
               display(sarr,cnt);
           }
           else if(command.equalsIgnoreCase("grade"))
           {
               Student.setCommand(command);
               //performing sorting operation
           bubbleSort(sarr,cnt);
               display(sarr,cnt);
           }
           else if(command.equals("end"))
           {
               break;
           }
       }
      
       sc.close();
      
   } catch (FileNotFoundException e) {
   System.out.println("** File Not Found **");
   }

   }

   private static void display(Student[] sarr, int cnt) {
       for(int i=0;i<cnt;i++)
       {
           System.out.println(sarr[i]);
       }
      
   }

private static void bubbleSort(Comparable[] list,int size) {
  
for(int i=0;i<size-1;i++)
{
if(list[i].compareTo(list[i + 1]) > 0)
{
swap(list,i,i+1);
}
}
if(size-1>1)
{
bubbleSort(list, size-1);
}
  
}
private static void swap(Comparable[] list, int i, int j) {
Comparable tmp = list[i];
list[i] = list[j];
list[j] = tmp;
}
/** Sort an array of comparable objects using the Bubble sort algorithm */
public static void sort(Comparable[] list) {
Comparable currentMin;
int currentMinIndex;
// select subarray (the range of the array) where we bubble up the
// greatest in the subarray
for (int i = 0; i < list.length - 1; i++) {
// bubble up the greast in the subarray (in the range of the array)
for (int j = 0; j < list.length - i - 1; j++) {
if (list[j].compareTo(list[j + 1]) > 0) {
Comparable tmp = list[j];
list[j] = list[j + 1];
list[j + 1] = tmp;
}
}
}
}

}
___________________________

Output:

Enter command :print
John Smith 90
Sarah Barnes 75
Mark Riley 80
Laura Getz 72
Larry Smith 95
Frank Phelps 75
Mario Guzman 60
Marsha Grant 85

Enter command :sortfirst
Frank Phelps 75
John Smith 90
Larry Smith 95
Laura Getz 72
Mario Guzman 60
Mark Riley 80
Marsha Grant 85
Sarah Barnes 75

Enter command :sortlast
Sarah Barnes 75
Laura Getz 72
Marsha Grant 85
Mario Guzman 60
Frank Phelps 75
Mark Riley 80
John Smith 90
Larry Smith 95

Enter command :grade
Mario Guzman 60
Laura Getz 72
Sarah Barnes 75
Frank Phelps 75
Mark Riley 80
Marsha Grant 85
John Smith 90
Larry Smith 95

Enter command :end

_______________Could you plz rate me well.Thank You